Basics, basics, basics. You could call K&R’s book one basic book which every programmer should read. Nowadays lots of new programmers think that Ruby on Rails is all you need. If you just build basic CRUD web apps this is probably true. However, if you want to understand what’s really going on in your web server, operation system or music player, you should know C. K&R isn’t a introduction course into C programming but it will help you to get better at it, if you have some experience in C / programming.
I really love this book, mostly for its cool exercises (implementing tail, memory management, etc.). Always a recommendation!